Effective delivery of therapeutic proteins for clinical use is a major challenge to pharmaceutical science. Once in the blood stream, these proteins are constantly eliminated from circulation within a short time by different physiological processes, involving metabolism as well as clearance using normal pathways for protein elimination, such as (glomerular) filtration in the kidneys or proteolysis in blood. Once in the luminal gastrointestinal tract, these proteins are constantly digested by luminal proteases. The latter can be a limiting process affecting the half-life of proteins used as therapeutic agents in per-oral administration and either intravenous or intramuscular injection. The problems associated with these routes of administration of proteins are known and various strategies have been used in attempts to solve them.
A protein family that has been the focus of clinical work and effort to improve its administration and bio-assimilation is the blood coagulation factor family, which includes procoagulation factors, such as factor IX (FIX) and factor VIII (FVIII). Deficiencies in the levels of functional coagulation pathway proteins can cause mild to severe bleeding disorders. For example, hemophilia A and B are inherited diseases characterized by deficiencies in FVIII and FIX polypeptides, respectively. The underlying cause of the deficiencies is frequently the result of mutations in FVIII and FIX genes, both of which are located on the X chromosome. Traditional therapy for hemophilias often involves intravenous administration of pooled plasma or semi-purified coagulation factors from normal individuals. These preparations can be contaminated by pathogenic agents or viruses, such as infectious prions, HIV, parvovirus, hepatitis A, and hepatitis C. Hence, there is an urgent need for therapeutic agents that do not require the use of human serum.
Recombinantly produced FIX polypeptides have been approved for procoagulation treatment of hemophilia. Also of therapeutic interest are FIX polypeptides that lack peptidase activity and can have anticoagulant activities useful in the treatment of thrombolytic diseases. Hence, FIX along with other coagulation factors are important therapeutic agents for procoagulant and anticoagulation therapies. Since naturally occurring variants can have undesirable side effects as well as the problems of administration, bioavailability, and short half-life, there is a need to improve properties of FIX for its use as a biotherapeutic agent. Therefore, among the objects herein, it is an object to provide modified FIX polypeptides that have improved therapeutic properties.